Centrifugal blowers are commonly known, in which an impeller is rotated to cause a fluid to flow in a spiral flow passage formed in a casing, which in turn feeds the fluid under centrifugal force.
In such a centrifugal blower, a pressure differential arises between a start point of the spiral flow passage and an end point where one turn of the spiral flow passage from the start point terminates. The start point region and the end point region of the spiral flow passage are adjacent to each other, and a phenomenon arises in which the fluid flows backward from the start point, where the pressure is low, toward the end point, where the pressure is high.
This phenomenon is likely to arise during operation in comparatively low flow rate ranges, and is a factor in the occurrence of stalling, which hampers the performance of the centrifugal blower. There is a further problem in that such backflow forms a vortex, which produces low-frequency sound and thus increases noise.
Here, Patent Document 1 discloses a centrifugal blower in which a backflow suppression partition is provided in a casing. This backflow suppression partition aims to suppress the occurrence of backflow as described above.